In a conventional multi-needle sewing machine (for example, the multi-needle sewing machine disclosed in Japanese published unexamined patent application No. 09-000765), the sewing machine shown in the cross-sectional view of FIG. 5(A) is configured that an upper frame 2 is disposed above a machine table 1 extending lengthwise in the horizontal direction (in the depth direction of the figure) as is well known. Multiple machine heads 3 are disposed at equal intervals in the lateral direction (in the depth direction of the figure) on the front face (on the right side in FIG. 5(A)) of this upper frame 2. Each machine head 3 is equipped with a machine arm 5 secured to the front face of the upper fame 2 and a moving base frame 6 that is supported so as to be sidable in the lateral direction using a rail 4 provided on the front face of the machine arm 5. A needle bar drive mechanism 8 and a thread take-up arm drive mechanism 10, driven using a machine spindle 7 commonly passing through all the machine arms 5, are installed inside the machine arm 5 as shown in FIG. 5(A). The needle bar drive mechanism 8 comprises a needle bar drive cam 12 fitted on the machine spindle 7; a rod 13, the base portion of which is fitted on the needle bar drive cam 12; a drive arm 14, one end portion of which is pivotally supported using the machine arm 5, and the intermediate portion of which is connected to the rod 13; and a needle bar driver 16 connected to the end of the drive arm 14 and supported using a base needle bar 15 so as to be movable vertically, whereby the needle bar driver 16 is driven so as to be reciprocated vertically along the base needle bar 15 by the rotation of the machine spindle 7.
The thread take-up arm drive mechanism 10 comprises a thread take-up arm drive cam 17 fitted on the machine spindle 7; a thread take-up arm drive arm 18 that is pivotally supported using the machine arm 5 at its intermediate portion and rocked reciprocally using the thread take-up arm drive cam 17; and a drive gear 20 secured to the rocking-side end of the thread take-up arm drive arm 18, whereby the drive gear 20 is reciprocated vertically by the rotation of the machine spindle 7.
Next, machine units 37, each comprising a thread supply section (not shown), a thread take-up arm 22, a needle bar 21, etc. are disposed in the moving base frame 6 as shown in FIG. 5(A). The multiple sets of the machine units 37 are arranged in parallel as shown in FIG. 1. The machine units 37 are made selectable by providing the moving base frame 6 so as to be movable in the lateral direction with respect to the frame 2.
Next, the configuration of the machine unit will be described using FIG. 5 (A) showing one machine unit 37.
Multiple needle bars 21 arranged in the depth direction in the figure are provided in the needle bar mechanism section 6c of the moving base frame 6 so as to be movable vertically.
An engaging pin 23, directed backward, is protruded at the vertically central portion of each needle bar 21 as shown in FIG. 5(A). The engaging pin 23 of the needle bar 21 selected by the needle bar selection operation associated with the sliding of the moving base frame 6 described later is fitted in the engaging groove 16a formed in the front face of the needle bar driver 16 in the machine arm 5, whereby the needle bar 21 is reciprocated vertically via the needle bar driver 16 by the rotation of the spindle 7. Numeral 19 designates a presser foot having a well-known configuration.
In correspondence with each needle bar 21, the thread take-up arm 22 is rockably provided above the needle bar 21 in the thread take-up arm mechanism section 6b of the moving base frame 6.
A boss 22a secured to the base portion of each thread take-up arm 22 is rotatably fitted on a thread take-up arm shaft 24 that is supported on the moving base frame 6 along the sliding direction of the case. A driven gear 25 that can be meshed with the drive gear 20 provided at the rocking end of the thread take-up arm drive arm 18 is formed around the outer circumference of the boss 22a. In addition, a fitting groove 26 (FIG. 5(A)) that faces downward when the thread take-up arm 22 has a predetermined posture (a posture obtained when the thread take-up arm is located near the top dead center) is formed in each boss 22a, and this fitting groove 26 is slidably fitted on a thread take-up arm rail 27 that is secured to the upper face of the end of the machine arm 5 and extends in the sliding direction of the moving base frame 6. In other words, each thread take-up arm 22 is held in the posture obtained near the top dead center by fitting the fitting groove 26 on the thread take-up arm rail 27. Because this thread take-up arm rail 27 does not have a portion that acts on the front portion of the drive gear 20 of the thread take-up lever aim 18, the fitting groove 26 of the thread take-up arm 22 that acts on the front portion of the drive gear 20 so that the driven gear 25 is engaged with the drive gear 20 is away from the thread take-up arm rail 27, whereby the thread take-up arm 22 is reciprocated between the top dead center 22e and the bottom dead center 22f thereof by the reciprocating movement of the thread take-up lever drive arm 18 under the engagement between the drive gear 20 and the driven gear 25.
Next, numerals 31, 32, 34 and 35 indicated on the right side of the machine head 3 in FIG. 5(A) respectively designate thread guide eyes having through holes configured to facilitate thread passing as is well known, and the thread guide eyes are used to guide the thread (41 to 46). Numeral 41 designates the thread that goes from a spool (not shown) positioned above to the thread guide eye 31 as is well known, numeral 42 designates a first thread element going from the thread guide eye 31 to the thread guide eye 32 positioned below, numeral 43 designates a second thread element that makes a U-turn at the thread guide eye 32 and goes to the through hole 33 of the thread take-up arm 22 positioned above, numeral 44 designates a third thread element that makes a U-turn at the through hole 33 of the thread take-up arm 22 and goes to the thread guide eye 34 positioned below, numeral 45 designates a thread element going downward from the thread guide eye 34 to the thread guide eye 35, and numeral 46 designates a thread element that is supplied to a needle and goes from the thread guide eye 35 to the through hole of a needle 21a. 
Recently, for the purpose of raising the efficiency of sewing, the rotation speed of the machine spindle 7 is increased, and the vertical reciprocation speeds of the needle bar 21 and the thread take-up arm 22 are increased significantly. However, when the speed of the reciprocating operation of the thread take-up arm 22 is increased significantly, the following problems occur.
First, the sewing operation for cloth 29 will be described using the machine unit 37 of the above-mentioned conventional multi-needle sewing machine. As is well known, by the high-speed rotation of the spindle 7, the needle bar 21 is moved toward a thread-supplying hook 28, and the thread take-up arm 22 is reciprocated vigorously in the vertical direction between the top dead center position 22e and the bottom dead center position 22f at the timing shown in FIG. 6, whereby sewing is carried out while the thread 41 is drawn out to the cloth. During this sewing operation, when the thread take-up arm 22 is moved from the top dead center position 22e to the bottom dead center position 22f shown in the figure, the thread take-up arm 22 abruptly lowers in almost synchronization with but slightly behind the operation of the needle bar 21 (refer to the timing chart of FIG. 6).
The thread element in the upper portion of the thread (the second thread element 43) located between the through hole 33 of the thread take-up arm 22 located at the top dead center position 22e and the thread guide eye 32 positioned below and having a predetermined length is abruptly pulled downward along a lowering locus 33a by the abrupt lowering of the through hole 33 of the thread take-up arm 22 to the bottom dead center position 22f; hence oversupply occurs at the space 33b between the through hole 33 located at the bottom dead center 22f and the thread guide eye 32, thereby causing a phenomenon in which the second thread element becomes uncontrollable in the wide space 33b near the thread guide eye 32 while instantaneously making a small loop.
In that case, when sewing is carried out using an ordinary thread, the thread take-up arm 22 immediately rises toward the top dead center position 22e, thereby dissolving the problem of the above-mentioned oversupply.
However, various kinds of threads have been provided because of the development of chemical fibers, and various types of thread twisting, such as left twisting, right twisting, strong twisting and weak twisting, have become available; hence, the end of the loop is formed to have an acute angle owing to thread twisting (twining) at the moment of the “oversupply state” in the space 33b between the through hole 33 and the thread guide eye 32 depending on the property of the thread, and the end of the loop is twined narrowly. For example, the end of the loop is twined to have the state indicated by numeral 43b in FIG. 5 (B). When the thread take-up arm 22 immediately rises toward the top dead center 22e while this twined state remains, the twined (twisted) portion 43b of the thread is pulled and cut off, thereby causing a problem.